Cracking residual fractions containing salts



Jam 1953 J. H. MCCULLEY EIAL 2,626,892

CRACKING RESIDUAL FRACTIONS CONTAINING SALTS 1 Filed Dec. 9, 1950 eases 26 4 SOAKER nenucronv I I f I I 1 an s on. FRACTION 4 Mi I I I NAPHTHA 5 mlllnull' nr I8 I u I: u nu. n 27 ZHEATING on.

\v H B "R FRACTIONATOR 7 3 SEPARATOR 2 Rssmwu. CRUDE ,4 I I 1 4 1 PETROLEUM nucnon 11/: I: I: I d/:

:1 :l l l llll ll I l 5: l ll llyl i R a;

cox: dONTAINING SALTS PRESENT IN RESIDUE INVENTORS.

HerberbP. Dayton, y John H. McCuHey,

Patented Jan. 27, 1953 CRACKING RESIDUAL FRACTIONS CONTAINING SALTS John H. McCulley, Baytown, and Herbert P. Dayton, Channelview, Tex., assignors, by mesne assignments, to Standard Oil Development Company, Elizabeth, N. J a. corporation of Delaware Application December 9, 1950, Serial No. 199,952

3 Claims. 1

The present invention is directed to a process for cracking residual petroleum fractions containing salts. More particularly, the invention has to do with the cracking under thermal conditions of residual crude petroleum fractions which contain organic and inorganic salts in excess of the salts naturally occurring in the crude petroleum.

The invention may be briefly described as involving a cracking process in which a residual crude petroleum fraction containing organic and inorganic salts in excess of the salts naturally occurring in the crude petroleum is heated to a temperature in the range between 700 and 880 F., which is below the cracking temperature of the residual fraction. A refractory gas oil fraction boiling in the range from 600 to 700 F. is separately heated to a temperature in the range from 940 to 1050 F. The two separately heated fractions are then separately charged into a reaction zone maintained at a pressure in the range between 500 and 800 lbs/sq. in. gauge. The residual fraction and the gas oil fraction are proportioned so that the ratio of the two streams is in the range between about 1:1 to 1:1.4. By admixing the two separately heated streams in this ratio the residual fraction is heated to a cracking temperature and undergoes a cracking reaction while the refractory gas oil fraction is cracked to only a negligible extent, if any. A product is formed by cracking of the residual fraction including light hydrocarbons, fuel oil and coke. The coke contains substantially all of the salts present in the residual fraction. The light hydrocarbons and the fuel oil are separate- 1y recovered and the coke is discharged from the reaction zone.

The organic salts and inorganic salts and other deleterious'compounds present in the residual crude petroleum fraction in excess of those salts naturally occurring in the crude petroleum usually include sodium naphthenates, sodium sulfonates, calcium sulfate, sodium hydroxide, and other organic and inorganic constituents resulting from the treatment which the crude petroleum receives as it passes through a modern petroleum refinery. For example, the sodium naphthenates are present as a result of the reaction of the naphthenic acids originally present in the crude petroleum with sodium hydroxide and other alkaline materials. As a result the sodium naphthenate ultimately finds its way into the residual fractions, such as asphalt and the like. The sodium sulfonates result from the exhaustive treatment of petroleum fractions with strong sulfuric acid whereby a portion of the hydrocarbons are sulfonated. Following the sulfonation treatment, it is conventional to neutralize the sulfuric acid treated material with sodium hydroxide and the like which results in the formation of sodium sulfonates, some of which find their way ultimately into the heavier fractions. Calcium sulfates may also be encountered in the residual crude petroleum fractions.

Treatment with other reagents and neutralization with alkaline material will also result in the formation of inorganic and organic salts in the residual fractions forming a product in the modern petroleum refinery.

When efiorts were made to crack such fractions containing inorganic and organic salts under thermal conditions, it was found that the temperature to which the residual fraction must be heated in order to crack same resulted in severe coking taking place in the furnace tubes in which the residual petroleum fraction containing salts was heated. The tendency to form coke was so severe that it was practically impossible to crack such fractions heretofore. The feed stocks of the present invention may be residual fractions from the distillation of crude petroleum over sodium hydroxide resulting in what is known as caustic bottoms containing sodium naphthenate and sodium hydroxide; it may be a propane sludge oil which has been treated with lime or it may be an asphalt recovered from a product which had previously been treated with alkaline material or the feed stock may be a heavy residuum which contains inorganic and organic salts in excess of those normally present in the crude petroleum and resulting from prior processing operations.

Typical feed stocks for the present invention and constituents thereof are shown in Table I.

The feed stocks such as those illustrated in the foregoing table will usually have a salt content no greater than 0.8 weight per cent. It is practically impossible to crack such fractions thermally without severe coking taking place in the furnace tubes which results in a very short time of operation.

In accordance with the present invention the feed stocks, such as illustrated before, are heated at a temperature in the range given and then cracked in a suitable reaction zone as a soaker, the heat for cracking being supplied by separately heating a refractory gas oil to a temperature in the range mentioned before above the cracking temperature of the salt containing fraction to cause cracking of the residual fraction in the soaker in admixture with the gas oil fraction.

The invention will be further illustrated by reference to the drawing in which the single figure is a diagram of a preferred mode of operation.

Referring now to the drawing, numerals I i and I2 designate, respectively, furnaces containing coils I3 and I4. Line I5 introduces into the system a residual crude petroleum fraction containing organic and inorganic salts, such as sodium naphthenates and sodium sulfonates, which on passage through coil i3 is heated to a temperature in the range between 700 and 880 F. The heated residual crude petroleum fraction then discharges from coil I3 by line I6 and is introduced thereby into soaker or reaction zone H.

A refractory gas oil fraction such as a cycle oil boiling in the range between 600 and 700 F.

and which may be obtained from a thermal or catalytic cracking operation and having a gravity from 26 to 36 API is introduced into the system by line I8 and is heated on passage through coil I4 to a temperature in the range between 940 and 1050" F. The heated refractory gas oil then passes outwardly from coil I4 by line I9 and is introduced thereby into soaker or reaction zone I! where it admixes with the residual crude petroleum fraction and gives up heat thereto and allows the residual crude petroleum fraction to be cracked to lighter products and to produce coke. The temperature in soaker or reaction zone I! ordinarily will be in the range from 850 to 950 F. Under these conditions the residual crude petroleum fraction is cracked but the refractory gas oil fraction is of such a nature that it is not cracked at these temperatures to any great extent and passes outwardly therefrom with the lighter products issuing from soaker IT by line 20. The salt constituents originally present in the crude petroleum fraction may be found in the coke which is discharged from soaker I! by line 30. It is understood that soaker I! may comprise a plurality of soakers. Such soakers are usually in pairs and are used in a swinging operation, one soaker being on reaction cycle while the other soaker is off the reaction cycle and the contents thereof, mainly the coke, are discharged therefrom by means well known to the art.

The light products in line are discharged therefrom into tar separator 2I where a separation is made between the tarry constituents and the lighter hydrocarbons. Tar is removed from tar separator 2I by line 22, while the lighter constituent are discharged by line 23 into a fractionation zone 24 which may be provided with a heating means, if necessary, illustrated by coil 25. Fractionation zone 24 is shown as a single fractionating tower but may include a series or a plurality of fractionating towers. For simplicity of description fractionation zone 24 is illustrated as a single fractionating tower and is equipped with suitable baffling equipment, such as bell cap trays, to allow intimate contact between liquids and vapors. Conditions are adjusted in fractionation zone 24 to allow removal overhead of gases and other lighter components by line 26, to recover by line 21 a cracked naphtha fraction, and to remove by line 28 a heating oil fraction which suitably may be used as a fuel in domestic or industrial installations. The refractory gas oil is withdrawn by line 29 and may suitably be recycled to the process, if desired.

The refractory gas oil fraction will usually be fractionated so that it contains negligible materials boiling about 720 F. and it is admixed with the residual crude petroleum fraction in an amount in the range from about 1.0 to 1.4 barrels of recycled gas oil per barrel of residual crude petroleum.

The amount of coke produced in the cracking reaction of the crude petroleum residue containing inorganic and organic salts amounts from ,2% to .8% by weight of the crude petroleum residue. Substantially all of the salts or ash components in the crude petroleum residue is deposited in the coke layer.

The soakers employed in the present invention, although only one is shown in the drawing, are swung every one to three days. As a result of such operation the tar removed from the tar separator contained a relatively small percentage of ash constituents by virtue of the removal of the salts with the coke.

Although not illustrated in the drawing it may be desirable to add to the stream in line I6 a small amount of a lower boiling point hydrocarbon to correct the viscosity of the crude petroleum residual and to facilitate pumping thereof. If desirable, an amount in the range of 10% and 40% of a viscosity corrector may be added thereto. A suitable amount is about 30% of the fresh feed.

It is desirable that the refractory gas oil stock be injected into the reactor or soaker through a separate nozzle from the crude petroleum residua injection nozzle to allow the benefits of the present invention to be satisfactorily obtained. If the crude petroleum residue were admixed with the refractory gas oil prior to injection into the reaction zone there is danger that coke formation may occur on injection into the soaker.

The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and to secure by Letters Patent is:

1. A cracking process which comprises heating a neutralized residual fraction from crude petroleum having a salt content no greater than 0.8% by weight and containing organic and inorganic salts in excess of salts naturally present in the crude petroleum to a temperatur in the range between 700 to 880 F. and below the cracking temperature of said residual fraction, separately heating a refractory gas oil fraction boiling in the range from 600 to 700 F. to a temperature in the range between 940 and 1050 F., separately charging said residual frac tion and said gas oil fraction in a ratio in the range between 1:1 to 121.4, to a reaction zone maintained at a pressure in the range between 500 and 800 pounds per square inch gauge, admixing the two fractions to cause heating of said residual fraction and cracking of sam in the substantial absence of cracking of said gas oil fraction to form a product including light hydrocarbons, fuel oil, and coke containing substantially all of the salts present in said residual fraction, and separately recovering said light hydrocarbons and fuel oil and discharging said coke from said reaction zone.

2. A process in accordance with claim 1 in which the organic salts comprise sodium naphthenates and sulfonates.

3. A cracking process which comprises heating a neutralized residual fraction from crude petroleum having a salt content no greater than 0.8% by weight and containing organic and inorganic salts and other deleterious compounds and including sodium naphthenates and sodium hydroxide in excess of salts naturally present in the crude petroleum to a temperature in the range between 700 and 880 F. and below the cracking temperature of said residual fraction, separately heating a refractory gas oil fraction boiling in the range from 600 to 700 F. to a temperature in the range between 940 and 1050 F., separately charging said residual fraction and said gas oil fraction in a ratio in the range between 1:1 and 111.4 to a reaction zone maintained at a pressure in the range between 500 and JOHN H. MCCULLEY. HERBERT P. DAYTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,373,391 Day Mar. 29, 1921 1,388,629 Coast Aug. 23, 1921 1,408,698 Hanna Mar. 7, 1922 1,705,181 Egloff Mar. 12, 1929 1,986,775 Kaufman et a1 Jan. 1, 1935 1,997,980 Smith Apr. 16, 1935 2,070,680 Peterkin Feb. 16, 1937 

1. A CRACKING PROCESS WHICH COMPRISES HEATING A NEUTRALIZED RESIDUAL FRACTION FROM CRUDE PETROLEUM HAVING A SALT CONTENT NO GREATER THAN 0.8% BY WEIGHT AND CONTAINING ORGANIC AND INORGANIC SALTS IN EXCESS OF SALTS NATURALLY PRESENT IN THE CRUDE PETROLEUM TO A TEMPERATURE IN THE RANGE BETWEEN 700* TO 880* F. AND BELOW THE CRACKING TEMPERATURE OF SAID RESIDUAL FRACTION, SEPARATELY HEATING A REFRACTORY GAS OIL FRACTION BOILING IN THE RANGE FROM 600* TO 700* F. TO A TEMPERATURE IN THE RANGE BETWEEN 940* AND 1050* F., SEPARATELY CHARGING SAID RESIDUAL FRACTION AND SAID GAS OIL FRACTION IN A RATIO IN THE 